This invention relates to a method and apparatus for automatic recognition of marks on metal and other specular surfaces with varying roughness and reflectivity.
Metal parts such as aircraft engine turbine blades which have an impressed serial number or part number present a difficult problem to an automatic identification system. Commerically available optical character readers by themselves can only be used for recognizing high contrast characters on paper. Factory parts on the other hand have surfaces that may be anywhere from smooth to rough and that reflect light differently. The fundamental problem to be treated is the acquisition of a high contrast image from metallic or other specular surfaces under varying conditions of surface roughness and reflectivity. Once this image has been obtained, the data is properly formatted and transferred to the OCR unit. In general, this data must be of high contrast to simulate the type of image acquired from printer paper marking.